The invention relates to a method and device for determining a predicted image region and a method and device for reconstructing a predicted image region.
The digital transmission of video data with high resolution and refresh rate requires video coding methods with high compression efficiency. A transmission rate, with which a high image quality should be achieved, is hereby often predetermined for the video coding method.
Video coding methods widely used today are for example standardized as MPEG2, MPEG4, ITU H.261, H.263 and H.264 (MPEG—Motion-Picture Expert Group, ITU—International Telecommunication Union). These video coding methods are based on a hybrid approach, including a temporal prediction of image content (=motion compensation) in conjunction with a transformation, for example a DCT or ICT (DCT—Discrete Cosine Transformation, ICT—Integer Coded Transformation) and a quantization of the error signal remaining after the motion compensation and transformation. With these video coding methods essentially the parameters of the motion model (vectors, block mode) and the resulting coefficients of the residual error signal are transmitted.
An improvement in compression efficiency for the same image quality allows the data transmission rate for transmitting a compressed video sequence to be reduced. This can be achieved for example by improving prediction. Also refinement of a pixel grid from pixel to half-pixel accuracy allows an improvement in motion estimation and therefore motion compensation. A further increase in compression efficiency can be achieved by reducing block sizes, for which a respective prediction is carried out in the context of motion estimation or motion compensation. In addition to an inter-prediction, in other words the utilization of a correlation between images recorded at different times, an intra-prediction can also be used to increase compression efficiency. With this intra-prediction a prediction is carried out for an image region based on already coded and reconstructed image content of the current image.